In the treatment of patients with high energy x-ray teletherapy machines, there has been a longstanding problem of accurately positioning the patient in the irradiation portal of the teletherapy machine so as to provide maximum effective treatment of the patient's body portions to be treated, while minimizing radiation exposure to other portions. Utilizing present techniques, localization errors are frequent, on the order of about 30%. In addition, present monitoring techniques are slow, and expensive, and are not practiced on-line (that is during actual treatment) so that no direct feedback is provided.
Conventionally, the proper positioning of a patient in the irradiation portal of a radiation teletherapy machine is accomplished during a weekly session specifically for filming the patient for proper positioning, no therapy being practiced during such sessions. The patient is positioned on the treatment couch, between the x-ray source and a film cassette and then the teletherapy machine is actuated for a short period of time. The film cassette is processed and then is reviewed prior to the next therapy session.
According to the present invention, most of the limitations associated with prior art monitoring procedures for radiation teletherapy are overcome, and the longstanding problem in the art with respect to such monitoring is solved. According to the present invention it is possible to accurately position the patient during each treatment session so that the tumor bearing sites will receive precisely the prescribed radiation dosage, while surrounding areas will receive a minimum of radiation. Weekly filming sessions are eliminated as are the needs for film storage and processing space. Additionally, according to the present invention the images produced are much clearer than the images produced during filming sessions, further contributing to the accuracy of patient positioning.
According to the present invention on-line monitoring of the patient position is possible despite the fact that high-energy x-rays are being utilized for therapy as well as to practice the monitoring. The patient's position can be immediately readjusted during a therapy session with instant feedback to the therapy technician to provide accurate information for proper positioning.
According to the present invention there is provided a method for treating a patient with radiation therapy utilizing a radiation teletherapy machine having high-energy x-rays. In practicing the method, the patient is positioned in the irradiation portal of the radiation teletherapy machine in a supposed effective treatment position. Operation of the machine is then effected to provide pulses of high-energy x-rays for treatment. The several pulses of x-rays are automatically detected and transformed to electrical signals, preferably by utilizing a plurality of solid-state detectors covered by filtering means preventing the passage of low energy scattered radiation to the detectors, and positioned on the opposite side of the patient as to the radiation source. The electrical signals are immediately automatically converted to a readable display providing the landmarks of the irradiation portal. Then the patient's position as defined by the landmarks is compared to the predetermined desired position for effective treatment of the tumor, and if necessary the patient's position is immediately adjusted with respect to the irradiation portal so that it is proper for effective treatment. The provision of a readable display for a patient position may be repeated, with subsequent adjustment of the patient's position, until the exact position is obtained. Once the patient is in proper position the radiation therapy is continued to deliver the desired dosage of radiation to the patient.
According to the present invention there is also provided apparatus for on-line treatment monitoring for radiation teletherapy. The apparatus comprises a radiation teletherapy machine for emitting high-energy x-ray pulses in an irradiation portal, a patient treating couch, and detecting means for detecting high-energy x-rays emitted from the radiation teletherapy machine and transmitted through the patient, and transforming the x-rays detected into electrical signals. The detecting means are located on the opposite side of the patient treatment couch as the radiation teletherapy machine. The apparatus further comprises filtering means covering the detecting means for preventing low energy scattered radiation from reaching the detecting means, and means for converting the electrical signals produced by the detecting means to a readable display providing patient landmarks of the irradiation portal. Preferably the detecting means comprise a plurality of solid-state photon detectors, such as silicon, cadmium telluride, or mercuric iodide detectors. The detectors may be disposed in a two-dimensional matrix covering the irradiation portal, or one or more linear arrays of detectors may be provided. Where linear arrays are provided a stepping motor is utilized to move the array over at least a portion of the irradiation portal in sync with the emission of x-ray pulses from the radiation teletherapy machine.
The means for converting the electrical signals produced by the detecting means to a readable display preferably include the following: An amplifier associated with each detector. A sample and hold means associated with each detector. Means for connecting the sample and hold means to the radiation machine through a proper timing delay for controlling the sample and hold means. A multiplexer connected to the output of the sample and hold means. An analog/digital converter means operatively attached to the output of the multiplexer. Adding means operatively attached to the output from the analog/digital converter for summing the electrical signals from each detector for each pulse A microprocessor operatively connected to the adding means; and an eventual video output connected to the microprocessor.
It is the primary object of the present invention to provide a method and apparatus for maximizing the delivery of therapeutic radiation to a patient's tumor bearing site while minimizing the amount of radiation delivered to other portions of the patient's body, by providing on-line monitoring of the patient's position within the irradiation portal. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.